As is well known, a bowler purchases a new bowling ball in a form that is free from finger holes. In the usual case, the ball is sold with an index mark which is generally intended to be located centrally of the finger holes. Holes are drilled about the index mark, typically for receipt of the middle finger and the ring finger on one side of the index mark and a hole for the thumb on the opposite side thereof.
The holes may be bored to various diameters to fit the finger size of the bowler. Typically, thumb hole and finger hole diameters will range from 5/8 of an inch to 13/22 of an inch.
Other dimensions of concern include the "span" and the "bridge".
Span is the distance between the near edges of the thumb hole and either of the finger holes, whereas bridge is the distance between the near edges of the two finger holes. "Pitch" is still another parameter. Pitch is the distance between the center line of a finger or thumb hole and a parallel radius of the ball. As can be readily imagined, with the number of variables involved, drilling the finger holes in a bowling ball is not a job to be relegated to the ordinary man on the street.
Generally, then, the balls are purchased at stores that specialize in bowling goods and/or bowling "pro" shops where there is sufficient traffic in bowling ball sales to justify the presence of a ball drilling machine as well as an experienced operator for the drilling apparatus. In addition, it is necessary that there be a person in attendance who is knowledgeable in fitting a ball to a bowler so that the proper hole diameters, span, pitch and bridge may be determined to set the parameters for the drilling operation.
It is believed that the foregoing situation has deterred many bowlers from buying their own balls, the bowlers relying instead on so called "house" balls maintained in most bowling establishments for use by patrons who do not own their own balls. For example, frequenting such a store specializing in bowling goods to make the purchase of a bowling ball is a less likely occurrence than a person frequenting a mass merchandiser, discount warehouse or the like. Consequently, the purchase of a bowling ball by many is put off, or does not occur at all because of this factor.
The problem may be compounded because many such establishments are relatively small and do not have the personnel available to fit the ball and then drill it during a single visit by the patron. Frequently, the ball will be fitted during regular store hours, but will not be drilled until after store hours, necessitating a return trip by the purchaser to pick-up the drilled ball.
Thus, there is a real need for an inexpensive, simple and sure means for fitting a ball to a bowler and drilling the same.